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/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.search.aggregations.metrics;

import org.opensearch.common.util.Comparators;
import org.opensearch.search.aggregations.Aggregator;
import org.opensearch.search.internal.SearchContext;
import org.opensearch.search.sort.SortOrder;

import java.io.IOException;
import java.util.Map;

/**
 * Base class to aggregate all docs into a single numeric metric value.
 *
 * @opensearch.internal
 */
public abstract class NumericMetricsAggregator extends MetricsAggregator {

    private NumericMetricsAggregator(String name, SearchContext context, Aggregator parent, Map metadata)
        throws IOException {
        super(name, context, parent, metadata);
    }

    /**
     * Single numeric metric agg value
     *
     * @opensearch.internal
     */
    public abstract static class SingleValue extends NumericMetricsAggregator {

        protected SingleValue(String name, SearchContext context, Aggregator parent, Map metadata) throws IOException {
            super(name, context, parent, metadata);
        }

        public abstract double metric(long owningBucketOrd);

        @Override
        public BucketComparator bucketComparator(String key, SortOrder order) {
            if (key != null && false == "value".equals(key)) {
                throw new IllegalArgumentException(
                    "Ordering on a single-value metrics aggregation can only be done on its value. "
                        + "Either drop the key (a la \""
                        + name()
                        + "\") or change it to \"value\" (a la \""
                        + name()
                        + ".value\")"
                );
            }
            return (lhs, rhs) -> Comparators.compareDiscardNaN(metric(lhs), metric(rhs), order == SortOrder.ASC);
        }
    }

    /**
     * Multi numeric metric agg value
     *
     * @opensearch.internal
     */
    public abstract static class MultiValue extends NumericMetricsAggregator {

        protected MultiValue(String name, SearchContext context, Aggregator parent, Map metadata) throws IOException {
            super(name, context, parent, metadata);
        }

        public abstract boolean hasMetric(String name);

        public abstract double metric(String name, long owningBucketOrd);

        @Override
        public BucketComparator bucketComparator(String key, SortOrder order) {
            if (key == null) {
                throw new IllegalArgumentException("When ordering on a multi-value metrics aggregation a metric name must be specified.");
            }
            if (false == hasMetric(key)) {
                throw new IllegalArgumentException("Unknown metric name [" + key + "] on multi-value metrics aggregation [" + name() + "]");
            }
            // TODO it'd be faster replace hasMetric and metric with something that returned a function from long to double.
            return (lhs, rhs) -> Comparators.compareDiscardNaN(metric(key, lhs), metric(key, rhs), order == SortOrder.ASC);
        }
    }
}